GetMessages.groovy

ConfigFileAuthenticationDetailsProvider provider =  new ConfigFileAuthenticationDetailsProvider('/path/to/.oci/config', 'DEFAULT')
StreamClient client = new StreamClient(provider)
AtomicBoolean closed = new AtomicBoolean(false)

CreateGroupCursorDetails cursorDetails = CreateGroupCursorDetails.builder(
        .type(CreateGroupCursorDetails.Type.TrimHorizon)
        .commitOnGet(true)
        .groupName(this.groupName)
        .build()
CreateGroupCursorRequest groupCursorRequest = CreateGroupCursorRequest.builder()
        .streamId(streamId)
        .createGroupCursorDetails(cursorDetails)
        .build()

CreateGroupCursorResponse cursorResponse = this.client.createGroupCursor(groupCursorRequest)

GetMessagesRequest getRequest = GetMessagesRequest.builder()
        .cursor(cursorResponse.cursor.value)
        .streamId(this.streamId)
        .build()

while(!closed.get()) {
    def getResult = this.client.getMessages(getRequest)
    getResult.items.each { Message record ->
        def msg = new String(record.value, "UTF-8")
    }
    getRequest.cursor = getResult.opcNextCursor
    sleep(500)
}